This invention relates to an air bag module capable of variable air bag inflation.
It is well known in the prior art to provide an air bag module which includes an inflatable air bag for protection of a vehicle occupant. The air bag module typically includes an inflator for discharging inflator gas to inflate the air bag. Upon sensing certain predetermined vehicle conditions, such as a certain amount of vehicle deceleration, the inflator discharges a fixed amount of inflator gas and the air bag is deployed.
In some cases, it may be desirable to provide an inflator that has varied levels or stages of inflator gas output in response to the sensing of different vehicle or occupant conditions. Thus, it is also known in the prior art to provide a dual-stage inflator that can discharge predetermined amounts of gas at one or two levels. However, these dual-stage inflators are more complex than typical inflators and have the limitation of typically providing only two different levels of gas output. An inflator that discharges inflator gas at a wide range of levels is not readily available. Even if available, dual-stage or multi-stage inflators are complex to manufacture and add mass to the air bag module.
It has also been suggested in the prior art to provide an air bag module including a reaction canister which houses the inflator and air bag and which includes a valve member which is continually repositioned for opening, closing, or partially opening the vent openings on the reaction canister primarily in response to changes in ambient temperature by the use of a bimetallic spring, servo motor or solenoid valve. Thus, the amount of the discharging inflator gas expelled from the housing is controlled solely by the exact position of the valve member which must be carefully positioned for providing partial opening of the vent openings. In addition, the prior art teaches that the position of the valve member and the amount of venting is continually adjusted during vehicle use prior to activation of the inflator rather than only specifically at the time of air bag deployment. In addition, the use of a bimetallic spring, servomotor or solenoid takes time to move the valve member between the various positions and thus is continually being adjusted prior to activation of the inflator. This arrangement is also complex and adds mass to the module.
This invention provides advantages and alternatives over the prior art by providing a variable inflation device that provides a wide range of levels of inflator gas into the air bag. This can be accomplished with an inflator having a single output level for discharging inflator gas. Advantageously, this invention provides a lightweight device mounted on the inflator which can be activated nearly instantaneously to vary the amount of venting for the module and thus the level of inflator gas discharged into the air bag based upon occupant and vehicle conditions. Thus, the device need only be activated under circumstances in which the inflator is activated and not on a continual basis prior to inflator activation. Preferably, the level of inflator gas discharged into the air bag is varied based on the exact time that a vent opening in the housing is either opened or closed during inflator activation. Advantageously, the device may be expendable since it is only used once, if at all, during inflator activation. Furthermore, the device is compact and is mounted externally on the inflator such that the variable inflation device serves the dual purpose of attaching the inflator to the housing in addition to providing variable inflation. Furthermore, other than vent holes, the variable inflation device requires no modifications to the housing and is not limited by the shape of the housing. In addition, the variable inflation device may be used with traditional single stage inflators without internal modifications to the inflator.
These advantages are accomplished in the present invention by providing an air bag module for restraint of an occupant in a vehicle. The module includes an air bag -and an inflator being activatable to discharge inflator gas for inflating the air bag. The inflator has at least one discharge port through which inflator gas is discharged. A housing includes at least one inflator vent opening aligned with the discharge port. A variable inflation device is mounted on the inflator and includes a movable member alignable with the vent opening. The movable member is movable relative to the vent opening for opening and closing the vent opening at a predetermined time during inflator activation to control the amount of inflator gas discharged into the air bag and the amount of inflator gas expelled out through the vent opening of the housing. Preferably, the variable inflation device includes an initiator device being activatable during activation of the inflator to move the movable member relative to the vent opening at the predetermined time during inflator activation.
Thus, it will be appreciated that variable levels of inflation of the air bag can be achieved using a single inflator having only a single level of gas output in combination with at least one vent opening that is preferably either entirely opened or entirely closed at a predetermined time during discharge of inflator gas by a movable member in response to activation of the initiator device. Almost instantaneous control of the movable member is enabled by the use of the initiator device that reacts nearly instantaneously to the signal received from the vehicle sensors. It will also be appreciated that this system provides a relatively simple, cost effective, and lightweight solution to providing variable levels of air bag inflation from a single level inflator.